The present invention relates to a motor-driven compressor.
Generally, a motor-driven compressor includes a housing that accommodates a compression unit, which compresses refrigerant, and an electric motor, which drives the compression unit. A cover is coupled to the housing. A motor driving circuit, which drives the electric motor, is arranged between the housing and the cover. The motor driving circuit includes a flat circuit board and various types of electric components arranged on the circuit board. The housing includes an end wall having a through hole that receives a sealing terminal. The sealing terminal includes a metal terminal, which is electrically connected to the motor driving circuit, and an insulator, which fixes the metal terminal to the end wall of the housing and insulates the metal terminal from the end wall. The metal terminal includes an end electrically connected to the motor driving circuit by a cable. The other end of the metal terminal extends into the housing through the through hole and is electrically connected to a connector of the electric motor.
In the motor-driven compressor, the electric motor is driven when power, which is controlled by the motor driving circuit, is supplied to the electric motor through the metal terminal and the connector of the electric motor. The driven electric motor drives the compression unit to draw refrigerant into the housing, compress the refrigerant with the compression unit, and discharge the refrigerant out of the housing (into an external refrigerant circuit, for example).
The circuit board and the electric components may be combined with a coupling base to form a module that facilitates the maintenance of the motor driving circuit. In this case, the circuit board, which is connected in advance to one end of the metal terminal by a cable, and the electric components are coupled to the coupling base. The coupling base is coupled to the cover with bolts, and the cover is then coupled to the housing with bolts. When the cover is coupled to the housing, the other end of the metal terminal is extended through the through hole of the housing and electrically connected to the connector of the electric motor.
The motor driving circuit exchanges heat through the coupling base and the housing with the refrigerant that is drawn into the housing. This cools the motor driving circuit. However, when the hot highly-pressurized refrigerant compressed in the compression unit exchanges heat with the refrigerant drawn into the housing (pre-compressed refrigerant) through the housing, the refrigerant that is drawn into the housing is heated. This degrades the cooling capability of the motor driving circuit.
To solve this problem, Japanese Laid-Open Patent Publication No. 2002-188573 describes a coupling base (base plate) that includes an elongated groove and a refrigerant inlet, which is in communication with one end of the groove. The refrigerant inlet receives refrigerant from outside the housing (for example, from an external refrigerant circuit). The other end of the groove is in communication with the interior of housing through a refrigerant suction hole formed in the housing. The refrigerant supplied to the refrigerant inlet from outside the housing flows into the elongated groove and is drawn into the housing through the refrigerant suction hole. The refrigerant flowing through the elongated groove exchanges heat with the motor driving circuit through the coupling base. The refrigerant in the groove is not easily affected by the heat from the hot highly-pressurized refrigerant that is compressed in the compression unit. This improves the cooling capability of the motor driving circuit.
However, when coupling the coupling base to the housing in the structure described in the publication, the coupling base may rotate about the axis of the metal terminal relative to the housing. This may cause difficulties when coupling the coupling base to the housing.